// key = string to match or null
// klen = key length (or 0), or if null key then len is the array offset value
// json = json object or array
// jlen = length of json
// vlen = where to store return value length
// returns pointer to value and sets len to value length, or 0 if not found
// any parse error will set vlen to the position of the error
char *js0n(char *key, int klen, char *json, int jlen, int *vlen);
